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GCN Circular 6569

Subject
GRB070621: Swift XRT refined analysis
Date
2007-06-22T11:31:25Z (16 years ago)
From
Boris Sbarufatti at INAF-IASF-Pa <sbarufatti@ifc.inaf.it>
B. Sbarufatti (INAF-IASFPA), P. Romano, C. Guidorzi (Univ. Bicocca &  
INAF-OAB)
A. Moretti (INAF-OAB) report, on behalf of the Swift-XRT team

We have analysed the first three orbits of Swift XRT data  for GRB070621
(Sbarufatti et al., GCN Circ. 6560), consisting of 150 s in Window  
Timing
mode data and 1.3 ks in Photon Counting mode.

The UVOT enhanced XRT position (Sbarufatti et al., GCN Circ. 6567) is
RA, Dec = 323.79225, -24.81752 which is equivalent to:

RA (J2000):   21 35 10.14
Dec (J2000): -24 49 03.1

with an uncertainty of 2.0 arcsec (90% confidence).

The X-ray light curve exhibits an initial steep decay (index -3.8  
+/-0.1)
up to T+380 s. A flare is observed around T+150s. After the break, the
count-rate decays with a power-law index of -0.91 +/- 0.04. If the  
present
slow decay continues, the predicted count rate 24h after the trigger is
2.1E-2 counts/s, corresponding to  a flux of 1.8E-12 ergs cm^-2 s^-1.

The WT and PC spectra can be fitted simultaneously with an absorbed
power-law model with a photon index 2.5+/-0.3 and a column density
(4.4 +/- 0.9)E21 cm^-2, significantly in excess with respect to the
galactic value (3.5E20 cm^-2, Dickey & Lockman, 1990). The absorbed
(unabsorbed) fluxes are 8.4E-10 (2.2E-09) ergs cm^-2 s^-1 for
the WT spectrum and 1.4E-11 (3.6E-11) ergs cm^-2 s^-1  for
the PC spectrum.

This circular is an official product of the XRT team.
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